A. Field of the Invention
The invention relates to removal of metal contaminants from heavy hydrocarbon stocks such as high boiling point petroleum distillates, shale oils, tar, pitches, residues and crude oil by contacting the hydrocarbon with particulate active carbon which has been pretreated with a highly acidic oxidizing medium.
B. Background of the Invention
Catalytic conversion of heavy hydrocarbons such as shale oils, vacuum distillates from atmospheric distillation of crude petroleum and residual oils has long been technically difficult because of the presence of metal contaminants which result in severe catalyst deactivation. These metal contaminants, which most commonly are nickel and vanadium, generally are found to exist as organometallic compounds of relatively high molecular weight, for example as porphyrins. When a hydrocarbon containing organometallic compound is catalytically treated, the metals and coke become deposited on the catalyst resulting in rapid deactivation of the catalyst.
It has long been known to remove at least a portion of such metals from hydrocarbons by contacting them with various substances such as e.g. bauxite or with metal-containing porous media such as e.g. cobalt molybdate on alumina.